The present invention concerns an actuation device for a control cable for a bicycle gearshift, in particular a so-called bar-end device suitable for being mounted on the forward-facing end of racing bicycle handlebars.
A bicycle is normally provided with a rear derailleur associated with the chainset, which consists of a series of coaxial gear wheels (pinions), having different diameters and numbers of teeth, fixedly connected to the hub of the rear wheel.
A bicycle is typically also provided with a front derailleur associated with the crankset, which consists of a series of gear wheels (toothed crowns) having different diameters and numbers of teeth, associated with a pin of the bottom bracket assembly set in rotation by a pair of pedals.
In both cases, the derailleur engages a transmission chain extending in a closed loop between the chainset and the crankset, shifting the chain on gear wheels having different diameters and numbers of teeth, so as to obtain different transmission ratios.
In particular, the expression downward gearshifting is used when the chain goes from a gear wheel having a larger diameter to a gear wheel having a smaller diameter, and the expression upward gearshifting when the chain moves from a gear wheel having a smaller diameter to a gear wheel having a greater diameter. Regarding this, it should be noted with reference to the front derailleur that downward gearshifting corresponds to passing to a lower transmission ratio and upward gearshifting corresponds to passing to a higher transmission ratio, vice-versa with reference to the rear derailleur, downward gearshifting corresponds to passing to a higher transmission ratio and upward gearshifting corresponds to passing to a lower transmission ratio.
The movement in the two directions of a derailleur is obtained through an actuation device mounted so as to be easily operated by the cyclist; in the case of a so-called bar-end device, mounting takes place on the handlebars, at the ends thereof.
Conventionally, the actuation device for the front derailleur is located on the left handgrip of the handlebars, and vice-versa the actuation device for the rear derailleur is located on the right handgrip.
More specifically, in a mechanical gearshift, each derailleur is moved between the gear wheels, in a first direction by a pulling action exerted by a normally sheathed inextensible cable (commonly called Bowden cable), and in a second opposite direction by releasing the traction on the cable and/or by the elastic return action of a spring provided in the derailleur itself.
Normally, the direction in which the movement is caused by the release of the traction of the cable and/or by the return spring is that of downward gearshifting; vice-versa, the pulling action of the control cable takes place in the direction of upward gearshifting, in which the chain moves from a wheel having a smaller diameter to a wheel having a greater diameter.
In the actuation device, the control cable is actuated in traction or in release through winding and unwinding on a rotor element, commonly called cable-winding bobbin, the rotation of which is controlled by the cyclist with a suitable control lever. Single-lever control is made necessary by the positioning at the end of the handlebars, where it would be complex and not very practical to use two control levers, as it occurs—on the other hand—for different types of devices, located in different parts of the handlebars.
In any case, the actuation device must ensure that the bobbin is held still in rotation in a number of predetermined angular positions, corresponding to the different positions of the derailleur required by the different ratios, i.e. on the different gear wheels of the gearshift. This function is obtained with so-called indexers, a great many types of which are known in the field, variously acting between the bobbin and the fixed casing of the device.
In more conventional so-called bar-end devices, the single-lever control acts substantially directly on the cable-winding bobbin, so that each angular position of the cable-winding bobbin, as defined by the indexing means, corresponds to a precise angular position of the control lever.
The search for better aerodynamics in a competition has led to the provision of a quite complex control device, described in EP-1837275-A2, which is intended to return into the neutral position. It is the purpose of the present invention to provide a simplified device that allows the return of the control lever into its neutral position.